The long-term goal of this project is to elucidate the mechanism of cellular immunity and hypersensitivity. Such an understanding may allow the rational manipulation of these processes in certain human diseases in which hypersensitivity contributes to the pathogenesis or where enhanced immunity might prevent or alleviate the disease. Studies include the further characterization of the lymphocytes responsible for MIF production using antibodies to lymphocyte Ly 1, and Ly 2,3 antigens, and determination of whether or not murine MIF is the product of histocompatibility-immune response genes. Studies on the nutritional requirements for macrophage activation in vitro and the biochemical characterization of normal and mediator activated macrophage membranes will be continued. The nature of the serum blocking factor found in normal multigravid women will be investigated using affinity chromatography with anti-immunoglobulins of different classes and the specificity of the factor determined by absorption with lymphocytes bearing different histocompatibility antigens. BIBLIOGRAPHIC REFERENCES: Osteen, R.T., Piessens, W.F., David, J.R., and Churchill, W.H.: Multiple in vitro mechanisms of tumor cytotoxicity demonstrated in the line-l guinea pig hepatoma model. J. Natl. Cancer Inst. 55:873, 1975. Kuhner, A.L., and David, J.R.: Partial characterization of murine migration inhibitory factor (MIF). J. Immunol. 116:140, 1976.